The invention is directed generally to connectors, and more particularly to a connector pin assembly for use in terminating a fiber optic cable and concentrically aligning the cable optical fiber with respect to the outer dimension of the connector pin.
In recent years fiber optic light transmission systems, wherein a single optically conductive fiber or a multiplicity of parallel optically-conductive fibers are arranged to form a flexible light-conductive cable bundle for conveying light from one location to another, have come into increasing use, not only for providing illumination, but also for conveying data from one location to another. In the latter application, a light source is modulated with data to be transmitted at one end of the cable bundle, and the data is recovered at the other end of the cable bundle by a photo-sensitive detector. Since the data is conveyed by a medium not subject to radio frequency interference or detection, such light transmission systems are particularly well adapted for high security applications, such as found in the data processing and military communications field.
With the increasing use of fiber optic systems, the need has developed for a connector for connecting segments of light-conductive cable bundles with minimum detriment to the optical transmission path. Prior art connectors for this purpose have not been completely satisfactory, particularly where frequent connects and disconnects must be made under adverse environmental conditions, or where multiple fiber optic circuits must be connected to a single connector because of the difficulty of maintaining an accurate consistent alignment between the ends of coupled cable segments under such conditions.
It is generally well known that the tolerances are very strict in the interconnection of a pair of fiber optic cables. The terminal ends of the cables must be axially and angularly aligned and as close together as possible without touching to achieve efficient light transfer. The glass material which is commonly used as the light-conducting fiber core of the cables is very brittle, and touching of the cable terminal end faces results in abrasions to the end faces which results in consequent reduced light transfer efficiency.
Where fiber optic systems are used for conveying data from one location to another, it is well known that as the data frequency is increased, the diameters of the fiber optic cables must decrease. Data transmission frequencies have increased to a point where only a single optical fiber is utilized for conveying the data. As a result, although the tolerance percentages for interconnecting fiber optic cables comprising a single optical fiber remains the same as for fiber optic bundles to achieve efficient light transfer, the absolute tolerance magnitudes decrease greatly.
It has been found that extremely strict axial and angular alignment between a pair of fiber optic cables can be achieved by terminating the optical fibers of the cables in connector pin assemblies in such a way that the optical fibers are concentrically aligned with respect to the outer dimensions of the connector pins. When a pair of such connector pins are concentrically and accurately aligned, the ultimate result is that the optical fibers will likewise be angularly and axially aligned for efficient light transfer.
Many techniques have been devised for aligning the optical fibers of fiber optic cables. However, these prior techniques have not been totally satisfactory.
One such technique is described in a paper entitled "Connecting The Thread of Light" by Kenneth Fenton and Ronald McCartney, published by ELECTRONIC CONNECTOR STUDY GROUP, INC., which was presented on Oct. 20, 1976 at the Ninth Annual Symposium Proceedings at Cherry Hill, New Jersey. The alignment technique therein described utilizes three rods of equal diameter which are arranged in an equilateral triangle configuration parallel with the axis of the fiber core. The rod diameter is selected so that the three rods come into intimate contact with each other and the minimum diameter fiber at exactly the same time to trap the fiber, within the interstices of the three rods.
A tapered entry tube constructed of elastomeric material is utilized for holding the optical fiber within the rods. The optical fiber is placed within the three rods and then housed within the tapered tube. The three rods project from one side of the tube and an O-ring provides terminating pressure.
Although the authors have indicated limited success, there are three main shortcomings of this termination technique. The first shortcoming, as identified by the authors themselves, is that this termination technique is not suitable for terminating stepped index profile plastic clad pure fused silica core fibers. Secondly, because the three rods project from the connector, there is no protection against contamination for the fiber when the connector is unmated. Lastly, because the connector is formed from a plastic material, the connector has potential environmental temperature and chemical instabilities.
It is therefore a general object of the present invention to provide a new and improved connector pin assembly for concentrically aligning and terminating a fiber optic cable with respect to the outer dimension of the connector pin.
It is a further object of the present invention to provide a new and improved connector pin assembly which provides protection against contamination for the terminated optical fibers when the connector is unmated.
It is a further object of the present invention to provide a connector pin assembly which is capable of terminating any one of the known types of fiber optic cables and providing environmental stability to the optical fiber termination.
It is a still further object of the present invention to provide a new and improved method of concentrically aligning and terminating an optical fiber within a connector pin assembly.